Kapt'n Krooz'r is a green alien in an armed flying saucer, who is on a planet infested by monsters of various types. Shooting a monster with the ray-gun will cause the monster to freeze temporarily. If the second matching type monster is shot while the first is still frozen, then that pair disappears. Krooz'r may progress to the next level by ridding the screen of all monsters, and play continues until the Kapt'n is eventually overwhelmed and all three lives are lost.
The saucer is operated using a trackball to direct the saucer's motion, and a joystick which causes the saucer to fire in the given direction. After the initial screen, levels slowly add complications which increase the game's difficulty. An early obstacle is that shooting non-matching monsters will only cause the top halves of the monster to swap forming chimeras. Only shooting matching chimeras cause them to disappear.
At higher levels, shooting matching monsters cause them to split into baby monsters instead of disappearing. The baby monsters can't be removed until all of the adults have been dealt with. When the smaller monsters are removed, they revert to eggs which can still move around. These in turn cannot be removed until the last of the baby monsters are eliminated. If the current level is set in a cave, then the eggs that are shot may hatch into bats or demons, which cannot be destroyed until all eggs have been shot.
From Mobygames.com. Original Entry